Lexical Definition

‎ματαιόω‎ mataióō (mat-ah-yo'-o) to make futile G:V
from ‎μάταιος‎

become vain.

Usage: 6 forms in 8 verses
Form Translated As     In Verse(s)
ἐματαιώθησαν they became futile Rom.1.21
μεματαίωταί It is folly LXX.1Sam.13.13
μεματαίωμαι I have acted in folly LXX.1Sam.26.21
ματαιούσιν they frame in folly LXX.Jer.23.16
εματαιώθησαν acted in folly LXX.2Kgs.17.15LXX.Jer.2.5
εματαιώθην I acted in folly LXX.1Chr.21.8
I was in folly LXX.2Sam.24.10

Abbott-Smith

ματαιόω, -ῶ (< μάταιος), [in LXX: IV Ki 17:15, Je 2:5, al. הבל, etc.;]
to make vain, foolish: Ro 1:21.†

Abbott-Smith References

Book Refs
2 Kings 17:15
Jeremiah 2:5
Romans 1:21

Liddell-Scott-Jones

ματαιόω,

bring to naught, [Refs 5th c.BC+]

__2 ματαιοῦσιν ἑαυτοῖς ὅρασιν invent a vision of their own, [LXX]
__II more frequently in passive, to be brought to naught, οὐ ματαιωθήσεται τὰ ῥήματα[LXX]
__II.2 become foolish, act foolishly, ἐματαιώθην σφόδρα[LXX+NT]; μεματαίωταί σοι thou hast done foolishly, [LXX]

LSJ Scripture Refs: LXX.Jer.23.16LXX.Judg.6.4LXX.1Chr.21.8Rom.1.21LXX.1Kgs.13.13